1. Field of the Invention
The present invention relates generally to high performance structural resins for advanced aerospace applications. It relates in particular to a series of imide/arylene ether block copolymers which find special utility as adhesives and composites.
2. Description of Related Art
Polyimides are condensation polymers commonly synthesized by the reaction of aromatic dianhydrides with aromatic diamines. The intermediate poly(amic acid) is either thermally or chemically cyclodehydrated to form the polyimide which has a repeat unit of the general type ##STR1## Ar is a tetravalent aromatic radical, which can be as simple as a 1,2,4,5-tetrasubstituted benzene, or it may be a bis-4-(o-diphenylene) having the general structure ##STR2## where X=nil, O, S, SO.sub.2, C=O, etc. Ar may be any other appropriate tetravalent radical. Ar' is a divalent aromatic radical which may be 1,3-phenylene, 1,4-phenylene, 4,4'-biphenylene, 4,4'-oxydiphenylene, 4,4'-thiodiphenylene, 4,4'-carbonyldiphenylene, 4,4'-methanediphenylene or any other appropriate divalent radical.
Synthesis and characterization of polyimides has been extensively reported in the literature. The preparation of aromatic polyimides by reaction of an aromatic dianhydride with an aromatic diamine, followed by thermal cyclization was first reported in 1963 (G. M. Bower and L. W. Frost, J. Polym. Sci. A1, 3134 (1963)) with patents awarded in 1965 (W. M. Edwards, U.S. Pat. Nos. 3,179,614 and 3,179,634 and A. L. Endrey, U.S. Pat. Nos. 3,179,631 and 3,179,633). Several reviews on polyimides have been published (C. E. Sroog, "Polyimides" in Encyclopedia of Polymer Sci. and Technology [H. F. Mark, N. G. Gaylord and N. M. Bikales, ed.] Interscience Pub., New York, 1969, Vol. 11, pp. 247-272; N. A. Adrova, M. I. Bessonov, L. A. Lauis and A. P. Rudakov, Polyimides, Technomic Pub. Co., Inc., Stamford, CT, 1970).
Wholly aromatic polyimides are known for their exceptional thermal, thermooxdidative and chemical resistance but are generally difficult to process as structural adhesives or composite matrices. Several polyimides such as Kapton.RTM. (DuPont), PI-2080 (Upjohn), XU-218 (Ciba-Geigy), Ultem.RTM. (General Electric) and LaRC-TPI (Mitsui Toatsu) are commercially available and used as films, moldings, adhesives and composite matrices.
Poly(arylene ethers) are condensation polymers commonly synthesized by nucleophilic displacement of activated aromatic halides in polar solvents by alkali metal phenates to form a repeat unit of the general type ##STR3## wherein Ar is arylene and Y=C=O, SO.sub.2, ##STR4## Nucleophilic displacement reactions leading to high molecular weight poly(arylene ethers) were initially reported in 1958 (A. Kreuchumas, U.S. Pat. No. 2,822,351). Since then numerous papers and patents have appeared, such as: R. N. Johnson, et. al., J. Polym. Sci. A-1, 5, 2375 (1967); S. V. Vinogradova, et. al., Polym. Sci. USSR, 14, 2963 (1972); J. B. Rose, Polymer, 15, 456 (1974); T. E. Attwood et al., Polym. Prepr., 20(1), 191 (1979); T. E. Attwood, et. al., Polymer, 22, 1096 (1981); R. Viswanathan, et. al., Polymer, 25, 1927 (1984); P. M. Hergenrother, et. al., Polymer, 29, 258 (1988); M. E. B. Jones, British Patent 1,016,245; H. A. Vogel, British Patent 1,060,546; I. Goodman, et. al., British Patent 971,277 (1964); A. G. Farnham et. al., British Patent 1,078,234; and A. G. Farnham, U.S. Pat. No. 4,175,175.
Poly(arylene ethers) are known for their good mechanical properties, good thermooxidative stability, relative ease of processing, and solubility in common organic solvents. For certain applications, resistance to common organic solvents is a requirement. Several poly(arylene ethers) such as Udel.RTM. polysulfone (Amoco), Kadel.RTM. polyketone (Amoco), PEEK.RTM. polyetheretherketone (ICI) and Victrex.RTM. PES polyethersulfone (ICI) are commerically available and used as films, moldings, adhesives and composite matrices.
Amine terminated arylene ethers have been prepared by several different methods. The preparation of amine terminated polysulfone oligomers using p-aminophenol as the end-capping compound was reported in 1974 (J. H. Kawakami, et. al., J. Polym. Sci. Polym. Chem Ed., 12, 565 (1974)). More recently, the preparation of amine terminated polysulfone and poly(arylene ether ketone) oligomers using m-aminophenol and 4-aminophenyl-4'-hydroxyphenyl-2-2-isopropylidene has been reported (M. J. Jurek, et. al., Polym. Prepr., 26(2), 283 (1985); G. D. Lyle, et. al., Polym. Prepr., 28(1) 77 (1987)).
It is accordingly the primary object of the present invention to synthesize a series of block copolymers containing polyimide and poly(arylene ether) segments employing a wide variety of imide and arylene ether repeat units and varying block length to give copolymers with specific desired properties.